Hot blobs of magma
- the searing liquid rock beneath the Earth's crust - can spread
slow-moving ripples that soar hundreds of meters high across the Earth's
surface, a new study suggests.

This phenomenon, which works on geologic time scales, may explain
relatively rapid pre-historical changes in sea level that occurred
without the typical waxing and waning of the polar ice sheets,
which hold and release water on scales of thousands and millions of
years. This unexplained sea
level rise is one of geology's oldest mysteries.

During the Paleogene era (65 million to 23 million
years ago), the land under Scotland moved up and down like a geological yo-yo. The
surface rippled up to 1,640 feet (500 meters) over the course of only a
million years - a relatively short time span, geologically-speaking.

"It appears to be caused by something deep
within the Earth, moving sideways - almost like rats running underneath a
carpet," said study author Bryan Lovell of the University of Cambridge.

The sideways movement is actually caused by
what's known as convection
currents in the mantle. These currents are created when
the cooler, denser material in the mantle sinks and the warmer, less
dense material rises.

"The hot blob would have spread out from the
center of the hot spot rather like a doughnut," Lovell said.

A magma hot spot beneath Iceland, known as the Iceland plume, which is
responsible for the European island's volcanic activity,
could be behind this movement.

Data from oil exploration near the Iceland
magma plume has revealed that a blob in the Earth's flowing mantle
caused a pulse beneath the North Atlantic about 55 million years ago.
This pulse raised and lowered the land surface and the sea floor in a
rippling effect

Although scientists were confident that hot
blobs exist in the mantle, evidence for the ripples at the Earth's
surface have been hard to spot. While the Scotland uplift is the only
example of the hot blob effect, Lovell said the movement is a natural
effect of mantle
convection, so there's no reason to think it isn't happening all
the time, even now.

"I'm delighted that we have what appears to
be a decent geophysical explanation for such a longstanding and
significant geological problem," Lovell said. "I hope we'll be able to
collect more observations from the geological record that will explain
otherwise cryptic features of the Earth's mantle."

The study was detailed in the June 25 edition
of the Journal of the Geological Society.